DESCRIPTION (Verbatim from the Applicant's Abstract): A 3-dimensional ultrasound imaging method will be developed to provide detailed anatomic and physiologic information about vein bypass grafts which have been placed to restore blood flow past an occluded artery in the leg. This method will replace X-ray contrast angiography and conventional ultrasonic duplex scanning, to provide complete information essential for monitoring the performance of the bypass. The 3-dimensional flow images created by this new method will allow evaluation of the inflow native artery which supplies the blood, the bypass graft, and the outflow native artery that carries the blood on to the foot and other tissues. Changes in the inflow, bypass and outflow segments will be studied over the first year after graft placement. The method will allow the examiner to study normal arterial pathway remodeling as well as the development of pathologic stenoses. More than 100,000 lower extremity bypass grafts are placed in the United States each year. Over 30,000 of these fail within 4 years. By developing methods to detect the early indicators of impending failure, this project offers the opportunity to extend the useful life of the grafts by permitting early treatment of the lesions.